1. Field of the Invention
The present invention generally relates to an apparatus and a system for irradiating food, and more specifically to a conveying and irradiation system, and a method for using the same, which can be adapted for use in existing buildings such as food packing houses to irradiate food for purposes of, e.g., disinfestation of produce.
2. Discussion of Material and/or Information
Numerous methods are known for disinfesting food, the most well known of which is the spraying of food with disinfectants and a variety of other fumigants. These methods have become disfavored in recent years, however, due to possible injury to the food and consumers; perhaps the best example of this is the ban imposed by the U.S. Environmental Protection Agency against the use of ethylene dibromide fumigation techniques. Other fumigants have similarly been earmarked by regulatory agencies for restricted use (if any), and presently existing substitute treatment methods have been ineffectual or have impaired the quality of the food products treated.
Although the U.S. Food and Drug Administration (i.e., the FDA) has previously approved the use of radiation for disinfestation of certain types of food, it has recently approved the irradiation of pork as well as the irradiation disinfestation of produce at low doses of radiation, i.e., at dosages of radiation up to 100 kilorads. In addition, the FDA, prior to 1985, approved the use of irradiation for wheat flour and grain, and potatoes. Further, countries outside of the U.S. have used irradiation to disinfest food for even longer periods.
Presently, food manufacturers and packers can use the several service irradiation plants throughout the U.S., which plants provide radiation services on a "pay as you go" toll basis to food production and packaging companies. Such toll may include, e.g., the salary of any U.S.D.A. or other inspectors who may be required.
None of the existing irradiators, however, are capable of being easily and relatively inexpensively integrated into present food production and packaging facilities. Thus, absent substantial additional expense, it is not presently possible for food production and packaging facilities and manufacturers to maintain complete quality control over their finished products via the use of in-house irradiators.
The present invention is designed to overcome the above defects and numerous other deficiencies in prior art irradiators, as well as to satisfy numerous needs of those in the food manufacturing and packaging/production industries.
Most conventional irradiators use storage pools for radioactive source materials when they are in their shutdown condition. These systems require an elaborate source raising system to lift radioactive cobalt-60 or cesium-137 source materials up from a pool to a cell located above the pool. In this fashion, the radioactive source is presented for irradiating products by using conveyor arrangements which are capable of carrying products through labyrinths which are positioned within concrete shielding walls around the cell, and then into close proximity to source materials. Such irradiator systems are disadvantageous because they require very heavy concrete shielding to completely enclose the source cell and the labyrinths which are used to convey materials into the cells. Such systems are referred to as "cell-type irradiators", and are capable of irradiating materials either in packages or in-the form of fully loaded pallets. These systems are cumbersome and heavily shielded irradiators which require extremely heavy structural members to support the heavy shielded roofing system and cell members, both of which generally comprise substantial amounts of concrete.
These types of irradiators are also disadvantageous in that extremely complex interlocking systems are necessary to prevent inadvertent admission of personnel into the irradiation cell while the source material is being elevated into (or is already in place within) its irradiation position. As a result, these irradiators require personnel barriers and automatic shutdown devices positioned along the labyrinths to automatically move the radioactive source material back to the source storage pool whenever anyone enters the cell. Even in such cases, because of the complexity of such safety systems, the interlocks can be bypassed or become inoperative, and personnel may still enter the cells and become (dangerously) exposed to high radiation levels. For these reasons, operation of these conventional irradiators generally requires constant attendance by highly qualified operating personnel.
Yet another disadvantage of conventional irradiating apparatus is that the cell into which the radioactive sources are raised includes a large volume of air which is subject to constant irradiation; this results in a relatively high production of ozone and nitrogen oxides, all of which are gaseous in form and generally toxic to plant personnel. These gases can also cause damage to various materials located in the cells.
Many of these disadvantages are overcome by the present packing house food irradiator and system of irradiating food, e.g., the present system eliminates or minimizes the large amount of expensive concrete shielding and the use of a cell system found in prior systems, as it instead maintains its source materials within the pool both during normal operation and during shutdown conditions.
The present system permits the operation of food packaging conveyors and the irradiator by less skilled personnel than can operate present conveyors. The system also permits complete physical removal of moving parts of the conveying equipment for replacement or repair without the necessity of shutting down and draining the pool, as the conveyor system is maintained within its own casing. The ductwork used in the irradiation chambers of the present device provides for the circulation of air which can be at a controlled temperature in order to maintain a desired temperature for food products traversing this system. The air circulating through the conveyor can also be provided with a make-up supply in order to minimize, if not eliminate, the concentration and generation of ozone, gaseous nitrogen oxides, and other noxious fumes.
The present invention will also be capable of providing irradiation treatment to food products at a high (and easily controlled) throughput capacity and at substantially lower capital and operating costs than existing irradiation service plants which could be used to irradiate food. These existing plants have been designed to provide high dose irradiation sterilization of medical products and irradiation sufficient to pasteurize and sterilize other food products, such as fish and red meats. The present irradiator is a relatively small and low cost irradiator which can be directly used in the process line of a food manufacturer or packager after packaging of a given product is complete. An area on the order of only 250-400 square feet is necessary for positioning the present irradiator within an integrated food packing house.